The present invention concerns a method for assembling and fixing a casing ring in a watch case, said case including a back cover and a middle part. It also concerns a casing ring manufactured to satisfy this assembly method.
Assembling a casing ring in a watch case has already been proposed, the ring being designed in such a way that it contains, in itself, all the means which fix it to the case without it being necessary to use additional means, such as, for example, screws or fixing clamps.
The document CH 688 926 discloses a clockwork movement housed in a casing ring whose periphery has raised portions and whose peripheral wall has recesses situated facing these raised portions so as to allow the ring to be deformed elastically in the raised portions regions when the ring is introduced into the case. It is thus possible to obtain perfect radial fitting of the movement in its case without it being necessary to respect strict tolerances. This document also proposes means for positioning the height of the ring with respect to the case, the axial fitting of such means being also achieved by raised portions which abut against the back cover of the case, these raised portions being followed by recesses made in the thickness of the ring and allowing said raised portions to be deformed elastically. The vertical play of the ring with respect to the case can thus be regained.
The design described above has several drawbacks. It will be mentioned first of all that the presence of the recesses necessary to allow the raised portions to be deformed elastically results in a ring of large thickness, and thus to a watch of large diameter for a given movement. It will be mentioned next that, if it is in fact possible to obtain perfect radial fitting of the movement in its case, it is not possible to assure a determined and precise radial positioning of the movement with respect to the case. Finally, it will be observed that if the vertical play of the ring with respect to the case is regained, it is at the cost of a constant thrust of the ring against the crystal which is then liable to be driven out of the middle part.
In order to avoid the aforecited drawbacks, the method for assembling and fixing the casing ring according to the invention is characterised in that it includes the following series of steps:
providing a casing ring made of a plastically deformable material, said ring being provided with integrated means forming a single piece with the ring and capable of positioning it with respect to the case;
introducing the ring into the case, which causes said positioning means to be deformed plastically; and
interrupting the introduction when the ring occupies a determined position with respect to the case.
Thus, it is clear that the method of the invention also relies on a material able to be deformed plastically, and not elastically, as a result of which the aforementioned drawbacks can be avoided. The ring is then of small thickness, it can be positioned precisely in the case and does not exert any thrust tending to push the crystal out of its housing.
The present invention also concerns a casing ring manufactured to satisfy the assembly method described above.